Basic and translational research in hematology has been at the cutting edge of recent advances in our understanding of the molecular pathophysiology of disease. The former Harvard Medical School Training Program in Molecular Hematology had a distinguished 25-year track record in training graduate students and postdoctoral fellows in the study of blood and its disorders, with many graduates of the program going on to highly successful academic careers. The past 25 years have seen many changes in the landscape of hematology-oncology in the Harvard Medical area, with the merging of the Hematology program at the Brigham and Women's Hospital with the oncology programs at the Massachusetts General Hospital and the Dana-Farber to form a combined Hematology-Oncology fellowship. This has had many positive effects on the opportunities for clinical and research training, complemented by a proliferation of training programs. At the same time, an explosion of new technologies has ushered in an era in biomedical research that offers exciting opportunities for major breakthroughs in our understanding of human disease, offering hope for new clinical paradigms that can transform the treatment of many hematologic disorders. However, the loss of a dedicated Hematology fellowship has made us acutely aware of the importance of nurturing physician scientists dedicated to the study of hematology. Indeed, the disappearance of free-standing hematology fellowships nationwide and the shrinking numbers of Hematology trainees signals an urgent need to encourage future academic hematologists. Therefore, in this new application, we seek to extend the success of the previous Hematology training program through a newly configured faculty and a more defined focus. The program will be limited to postdoctoral positions, and the selection process will place high priority on trainin physician- scientists focused on hematology. Potential candidates will be nominated by a potential preceptor or program leader, and applications will be reviewed by a Steering Committee. Final appointments will be made by the Program Directors. The primary site of training will be the preceptor's laboratory, but each trainee will be expected to participate in relevant seminars and courses within the HMS community. Each trainee will also assemble a training committee that will monitor research progress with annual formal presentations. We will strongly encourage the investigation of benign hematologic disorders in the areas of red cell disorders, iron metabolism, hemostasis and thrombosis, and neutrophil disorders, as well as hematologic malignancies such as leukemia, myelodysplasia, and myeloproliferative neoplasms. This strict focus on Hematology will distinguish this grant from other Harvard-related training grants, fulfilling a need that is not answered by any other training grant within adult medicine. (End of Abstract)